A user uses a computer to access a web service (e.g., an online banking portal) provided via a website. Before providing access to the web service, the website often requires the user to use the computer to enter secret authentication information (e.g., a password). The website provides the access to the web service after the computer transmits the secret authentication information to a web server associated with the website and the user is authenticated based on the secret authentication information. The user is subjected to man-in-the-middle (MITM) attacks when the secret authentication information is being transmitted from the computer to the web server. An MITM attack may include an attacker stealing (i.e., intercepting) the secret authentication information when the secret authentication information is transmitted.